/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.language;

import com.mlizhi.base.codec.EncoderException;
import com.mlizhi.base.codec.StringEncoder;


/**
 * Utility methods for {@link Soundex} and {@link RefinedSoundex} classes.
 * 
 * @author Apache Software Foundation
 * @version $Id: SoundexUtils.java 658834 2008-05-21 19:57:51Z niallp $
 * @since 1.3
 */
final class SoundexUtils {

/**
 * Cleans up the input string before Soundex processing by only returning
 * upper case letters.
 * 
 * @param str
 *  The String to clean.
 * @return A clean String.
 */
static String clean(String str) {
if (str == null || str.length() == 0) {
return str;
}
int len = str.length();
char[] chars = new char[len];
int count = 0;
for (int i = 0; i < len; i++) {
if (Character.isLetter(str.charAt(i))) {
chars[count++] = str.charAt(i);
}
}
if (count == len) {
return str.toUpperCase(java.util.Locale.ENGLISH);
}
return new String(chars, 0, count).toUpperCase(java.util.Locale.ENGLISH);
}

/**
 * Encodes the Strings and returns the number of characters in the two
 * encoded Strings that are the same.
 * <ul>
 * <li>For Soundex, this return value ranges from 0 through 4: 0 indicates
 * little or no similarity, and 4 indicates strong similarity or identical
 * values.</li>
 * <li>For refined Soundex, the return value can be greater than 4.</li>
 * </ul>
 * 
 * @param encoder
 *  The encoder to use to encode the Strings.
 * @param s1
 *  A String that will be encoded and compared.
 * @param s2
 *  A String that will be encoded and compared.
 * @return The number of characters in the two Soundex encoded Strings that
 * are the same.
 * 
 * @see #differenceEncoded(String,String)
 * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp">
 *  MS T-SQL DIFFERENCE</a>
 * 
 * @throws EncoderException
 *  if an error occurs encoding one of the strings
 */
static int difference(StringEncoder encoder, String s1, String s2) throws EncoderException {
return differenceEncoded(encoder.encode(s1), encoder.encode(s2));
}

/**
 * Returns the number of characters in the two Soundex encoded Strings that
 * are the same.
 * <ul>
 * <li>For Soundex, this return value ranges from 0 through 4: 0 indicates
 * little or no similarity, and 4 indicates strong similarity or identical
 * values.</li>
 * <li>For refined Soundex, the return value can be greater than 4.</li>
 * </ul>
 * 
 * @param es1
 *  An encoded String.
 * @param es2
 *  An encoded String.
 * @return The number of characters in the two Soundex encoded Strings that
 * are the same.
 * 
 * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp">
 *  MS T-SQL DIFFERENCE</a>
 */
static int differenceEncoded(String es1, String es2) {

if (es1 == null || es2 == null) {
return 0;
}
int lengthToMatch = Math.min(es1.length(), es2.length());
int diff = 0;
for (int i = 0; i < lengthToMatch; i++) {
if (es1.charAt(i) == es2.charAt(i)) {
diff++;
}
}
return diff;
}

}
